Theory and practice of botanical classification: Cladistics, phenetics and classical approaches?critical summary: Botanical systematics in 1987

Abstract

Aristotelian principles still dominate botanical classification. Biological classification has undergone a major transformation during the period fromAdanson (1763) toDarwin (1859), from essentialism and the practice of downward classification, to empiricism and upward classification. The polythetic class was conceptualized during the 1950s. Interest in the species problem generated data from many different disciplines, the most recent being DNA systematics. These many disciplines have contributed to our understanding of evolutionary processes and to improved classifications. Many different phylogenetic models were developed and for different kinds of data. These models formed the basis of many algorithms to infer phylogenetic trees, some widely available in computer packages. This became possible with rapid growth of computer technology. These developments in turn catalyzed the formulation of divergent philosophical principles and approaches to classification. For instance, should methodological principles be divorced from knowledge about evolutionary processes? These approaches are discussed along with problems of reticulate evolution, intra-OTU-variation, homology, and other issues in the light of existing methodologies and their impact on classification. The next important direction in addition to development of new classificatory algorithms is the synthesis of various elements of different methodologies presently used in isolation.